Vertical solid shaft pumps are primarily used for industrial and utility water and sewage deep well applications. Typically, vertical solid shaft pump motors are either of the open drip-proof fan-cooled configuration or canned submersible solid shaft motor drives. Open drip-proof motors are suited for dry pit locations only and do not meet the requirements for submersible and explosion proof applications.
Submersible motors, which are cooled to some degree solely by exposure to the submersible environment, tend to overheat when operated continuously in open air. If the submersible environment is not sufficient to adequately cool the submersible motor, or if the motor is to be used in open air, additional cooling means are typically provided. A conventional liquid cooling system is illustrated in FIG. 1. The motor 10 is encased in a liquid cooling jacket 12 having an inlet port 14 and an outlet port 16. This system is an open loop system from the perspective of the motor, in that it requires external provisions, such as a pump or other prime mover, for maintaining flow of the liquid coolant.
Solid shaft pump motors present particular challenges in order to accommodate motor cooling requirements that vary with their specific usage. A need exists for a solid shaft pump motor having a self-contained cooling system that is operable in a variety of environments, including dry pit, dry pit submersible and explosion proof conditions. Such a pump motor should meet minimum regulatory requirements, such as U/L, Factory Mutual, CE and CSA requirements, without the need for external cooling, and be capable of handling high reverse load that occurs during backflow.